Lamp unit



H. KREFFT May 14, 1935.

LAMP UNIT Filed March 5, 1934 f INVENTOR 26 W amW BY 7v 3% ATT RNEY Patented May 14, 1935 UNITED STATES LAMPUNIT Hermann Krefit, Berlin-Friedrichshagen, Germany, assignor to General Electric Company, a

corporation of New York Application March 5, 1934, Serial No. 714,161 In Germany March 15, 1933 4 Claims.

The present invention relates to lamp units generally and more particularly the invention relates to such units comprising two or more gaseous electric discharge lamp devices.

The object of the present invention is to improve the efficiency of a lamp unit comprising two or more gaseous electric discharge lamp devices. Another object oi the invention is to provide an efficient lamp unit emitting mixed light having high visual acuity value. A further object of the invention is to provide a lamp unit of the above type of a simple and compact structure. A still further object of the invention is to provide a concentrated, high intensity light source. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

In accordance with these objects the new and novel lamp unit comprises two gaseous electric discharge lamp devices one of which is a high voltage lamp the gaseous atmosphere of which has an operating pressure of 20 mm. or less and another of which is a low voltagelamp the gas- .eous filling of which has an operating pressure of 50 mm. or more. The gaseous atmosphere of the high voltage, low pressure lamp comprises a gas, a gas mixture, a vapor, or gas-vapor mixtures; the gaseous atmosphere of the low voltage,

high pressure lamp comprises only a vapor, or

a gas-vapor mixture. The high voltage low presvsure lamp is longer than the low voltage, high pressure lamp and is a more efllcient light emitter due to the fact that the voltage drop at the 35 cathode is less in proportion to the voltage drop along the positive column than in the shorter, high pressure lamp.v The long positive column of the low pressure lamp emits a great quantity of light and the light emitted thereby is dis- 40 tributed over the length of the positive column. The low pressure lamp is coiled or twisted around the high pressure lamp which makes the lamp unit very compact and concentrates the light emitting parts of the low pressure lamp. This 45 structure is very advantageous when the low pressure tube has a gaseous filling therein comprising a diflicultly vaporizable material, such as an alkali metal vapor, or cadmium, or magnesium, since the heat radiated by the high pressure tube 50 helps to maintain the metal vapor in the low pressure tube at an efiective pressure so that the low pressure lamp is operated at a lower current density than would be possible without the external heating by the high pressure lamp and s the low pressure lamp is a very efi'lcient light emitter. A heat conservator surrounding the lamps is provided to reduce the radiation of heat from the lamp unit which is of value in maintaining the vapor in the low pressure lamp at an effective pressure. The lamp unit is mounted 5 in a reflector, when desired, to direct the light emitted thereby.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in which,

Fig. 1 is a front elevational view of the new and. novel lamp unit, and

Fig. 2 is a side elevational viewthereof.

Referring to the drawing the, lamp unit comprises a disc-shaped support plate 2 attached to a 15 suspension hook I. A gaseous electric discharge lamp device having a straight container 5 is suspended from said plate 2 by support-strips 3 and 4 attached to the base 8 of said container 5. Said container 5 has two electrodes 6 and 1 sealed 2 therein at opposite ends thereof. Said electrodes 8 and 1 are electron emitting when heated and consist of a pressed, sintered mixture of electron emitting material, such as barium'oxide, and high melting point metal, such as tungsten. Said con- 25 tainer 5 has a gaseous filling therein consisting of a starting gas, such as argon, and an easily vaporizable material, such as mercury. Said elec-. trodes 6 and l are mounted on leads 6' and 1' respectively. Said leads 6 and 1 pass through the 30 plate 2 and said lead 6' passes through metal base 8 of said container 5 and said lead 1 passes through metal base 9 of said container 5. Said leads 6' and I are insulated from said bases 8 and 9 respectively. An auxiliary electrode 10 is mounted adjacent said electrode 6 to facilitate the starting of the main discharge between said electrodes 6 and I. Said auxiliary electrode I0 is connected to said lead I through a high resistance l0.

Another gaseous electric discharge lamp having a container II is suspended from said plate 2 by support strips l6 and I1. Said container II has a plurality of straight, parallel legs connecting by curved portions. The legs of said container I l are adjacent said container 5. Said container II has electrode chambers l2 and I3 at opposite ends thereof and electrodes I4 and l 5 are mounted in said electrode chambers 12 and I3 respectively. Said electrodes l4 and I5 are electron emitting when heated and consist of a coiled metal filament, such as a tungsten filament coated or impregnated with an electron emitting material, such as barium oxide. Current leads and I9 passing through plate 2 are connected to said voltage of the usual supply lines of commerce,

such as 110 or 220volts and the current load on this lamp is such that the gaseous filling is at a pressure of from 50 mm. to several hundred millimeters during the operation of the device. When desired the lamp having container 5 is of the high pressure, unsaturated vapor type. The lamp having container H operates on approximately the same voltage and the pressure of the gaseous atmosphere therein is mm. or less during the operation of thelamp. Said container 5 radiates a large amount of heat which helps to maintain the container l l at an elevated temperature and the metal vapor therein at an effective pressure during the operation of the lamp unit so that the lamp ll operates on a low current density and at high efliciency. The light emitted by the lamp unit is a mixture of the rays characteristic of mercury and sodium and has a high visual acuity value.- The lamp unit is an emcient, concentrated source of high intensity light useful in illuminating roads, airports and the like. Thelamp unit is easily repaired and cleaned as each of theelements 20, II and 5 are easily removable therefrom.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention, for example, when container H has a rare gas filling only a high voltage transformer is provided to operate the low pressure lampand said transformer is mounted on the reflector for the lamp .unit, when desired; the lamp having the container 5 is started into operation by applying a tainer u, when desired: the lamp 5 is connected in series with the lamp H to the secondary of the high voltage transformer, when desired; whenboth tubes are operated on alternating current the lamp 5 is connected in series with the primary I or the high voltage transformer which reduces the number of switches, when desired; said jacket 20 is double walled and the space between of said lamps being a low pressure metal vapor lamp and another of said lamps being a high pressure metal vapor lamp, said low pressure lamp surrounding said high pressure lamp, said lamps being mounted in adjacent, parallel posipressure' lamp.

2. A lamp unit comprising in combination, two or more gaseous electric discharge lamps, one of said lamps being a low pressure metal vapor lamp itons, said high pressure lamp heating said low:

and another, of said lamps being a high pressure metal vapor lamp, said low pressure lamp surrounding said high pressure lamp, said lamps being mounted in adjacent, parallel positions, said high pressure lamp heating said low pressure lamp, and a heat conservator enclosing sald' lamps. T 3. A lamp unit comprising in combination, two or more gaseous electric discharge lamps, one of said lamps being a low. pressure sodium lamp and another of said lamps being a high pressure mercury lamp, said low pressure lamp surrounding said high pressure lamp, said lamps being mounted in adjacent, parallel positions, said high pressure mercury lamp heating said low pressure sodium lamp.

4. A lamp unit comprising in combination, two I or more gaseous electric discharge lamps, one ofsaid lamps being a low' pressure cadmium lamp and another of said lamps being a high pressure mercury lamp, said low pressure lamp surrounding said high pressure lamp, said lamps being mountedliri adjacent, parallel positions, said high pressure mercury lamp heating said low pressure cadmium lamp.

' HERMANN KREFFT. 

